<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    let money = 100
    while (true) {
      let re = +prompt(`请选择您的操作：
      1.存款
      2.取款
      3.查看余额
      4.退出`)
      if (re === 4) {
        break
      }
      switch (re) {
        case 1:
          let save = +prompt('请输入存款金额')
          money += save
          break
        case 2:
          let send = +prompt('请输入取款金额')
          money = money - send
          break
        case 3:
          alert(`目前银行卡余额为：${money}`)
          break
        default:
          alert('没有此选项，请重新输入')
      }
    }



  </script>
</body>

</html>